How to Diagnose Mac Problems

Every Mac is made up of a small mountain of components, so when one isn’t working properly, the effects can sometimes be felt across the entire system. So often, the best first step is to suss out which component is on the fritz:Hardware Test

Get information about your hardware in a snap with the Apple Hardware Test.

The quickest way to check your system is with the Apple Hardware Test application, which is included with all new Macs. For Intel-based systems, insert the Mac OS X Install Disc 1 and hold down the D key while starting up. Within minutes, you’ll get a quick idea of where your system stands. (If your system shipped with OS X Lion, you’ll boot into an internet-based version of the test instead; see support.apple.com/kb/ht1509 for details.)

External Devices

In order to make sure the problem is actually with your Mac, shut down the computer, then disconnect all external hard drives and third-party peripherals. Restart with your original Apple keyboard and mouse attached (you still have them, right?) to see if the problem persists.RAM

Bad RAM is rare, but Rember can sniff it out for free.

Defective memory can cause system crashes or other instabilities. If you have third-party memory installed, shut down your system, remove it, and swap in the original sticks. If your particular issue goes away after restarting, it’s a likely sign of bad RAM that should be replaced. Freeware apps like Rember (kelleycomputing.net:16080/rember), which is a front end for the “memtest” Terminal command, can also quickly diagnose available system RAM.

Battery

Quickly learn about your battery’s health with the System Profiler.

Many problems with portable Macs—the most obvious being a sudden shutdown—can be traced to a bad battery. Head to the Power section of the System Profiler sidebar (Apple menu > About This Mac > More Info) and look for the battery-health data at the right; anything other than Normal means your battery should be replaced.

Which tells me that my old Skype 2.8 was likely the cause. Check Console for error messages first. Only then suspect hardware.

Secondly external peripheral are often an issue. The article is exactly right. Unplug everything and see if the problem goes away. A lot of times a flaky external drive or bad USB cord can make the whole system sick, and these kind of problems can look like something else inside the case.

The other point I'd like to add would be to recommend CoconutBattery. It's a bit of freeware that gives you a much better idea of the health of your battery. Rather than just "Normal" it tells you current charge state, the original design capacity and current capacity of the battery. So according to CoconutBattery my MacBook battery has a designed capacity of 4100mAh but currently it only can hold 3675mAh or 91%. That's actually not too bad considering it's a three year old battery that I have to admit I didn't treat as well as I should have. HINT: they like to be cycled. Don't leave them on the charger all the time.